Articulating expandable intervertebral implant

ABSTRACT

A spacer for separating bones of a joint includes a frame and a carriage. The carriage has ramped surfaces, and is slideably moveable in relation to the frame. A screw support is moveably connected to the frame to form a changeable angular orientation with respect to the frame. An actuating screw is supported by the screw support, and is connected to the carriage to cause the carriage to slideably move in relation to the frame when the actuating screw is rotated. Opposing endplates are configured to engage opposing bone of the joint, and each has ramped surfaces mateable with the ramped surfaces of the carriage. When the carriage is moved by rotation of the actuating screw, the ramped surfaces of the carriage and the endplates slide against each other, causing the endplates to move relatively apart, to increase the height of the spacer.

FIELD OF THE INVENTION

This invention relates to stabilizing adjacent vertebrae of the spine byinserting an intervertebral spacer, and more particularly anintervertebral spacer that is adjustable in height, and a tooltherefore.

BACKGROUND OF THE INVENTION

The vertebral or spinal column (spine, backbone) is a flexible assemblyof vertebrae stacked on top of each other extending from the skull tothe pelvic bone which acts to support the axial skeleton and to protectthe spinal cord and nerves. The vertebrae are anatomically organizedinto four generalized body regions identified as cervical, thoracic,lumbar, and sacral; the cervical region including the top of the spinebeginning in the skull, the thoracic region spanning the torso, thelumbar region spanning the lower back, and the sacral region includingthe base of the spine ending with connection to the pelvic bone. Withthe exception of the first two cervical vertebrae, cushion-like discsseparate adjacent vertebrae, i.e. intervertebral discs.

The stability of the vertebral column during compression and movement ismaintained by the intervertebral discs. Each disc includes a gel-likecenter surrounded by a fibrous ring. The gel-like center, i.e. nucleuspulposus, provides strength such that the disc can absorb and distributeexternal loads and contains a mixture of type II-collagen dispersed in aproteoglycan matrix. The fibrous ring, or annulus fibrosus, providesstability during motion and contains laminated rings of type-I collagen.Thus, the annulus fibrosis and the nucleus pulposus are interdependent,as the annulus fibrosis contains the nucleus pulposus in place and thenucleus pulposus aligns the annulus fibrosus to accept and distributeexternal loads. The integrity of the composition and structure of theintervertebral disc is necessary to maintain normal functioning of theintervertebral disc.

Many factors can adversely alter the composition and structure of theintervertebral disc, such as normal physiological aging, mechanicalinjury/trauma, and/or disease, resulting in impairment or loss of discfunction. For example, the content of proteoglycan in the nucleuspulposus declines with age, thus, it follows that the ability of thenucleus pulposus to absorb water concurrently declines. Therefore, innormal aging the disc progressively dehydrates, resulting in a decreasein disc height and possible de-lamination of the annulus fibrosus.Mechanical injury can tear the annulus fibrosis allowing the gel-likematerial of the nucleus pulposus to extrude into the spinal canal andcompress neural elements. Growth of a spinal tumor can impinge upon thevertebrae and/or disc potentially compressing nerves.

Bones of the spine, and bony structures, generally, are susceptible to avariety of weaknesses that can affect their ability to provide supportand structure. Weaknesses in bony structures have numerous potentialcauses, including degenerative diseases, tumors, fractures, anddislocations. Advances in medicine and engineering have provided doctorswith a plurality of devices and techniques for alleviating or curingthese weaknesses.

In some cases, the spinal column, in particular, requires additionalsupport in order to address such weaknesses. One technique for providingsupport is to insert a spacer between adjacent vertebrae.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the disclosure, a spacer forseparating bones of a joint comprises a frame; a carriage slideablymoveable in relation to the frame, and having at least one rampedsurface; an actuating screw connected to the carriage and supported bythe frame, the actuating screw configured to cause the carriage toslideably move in relation to the frame when the actuating screw isrotated; a first endplate configured to engage a first bone of thejoint, and having at least one ramped surface mateable with the at leastone carriage ramped surface, whereby when the carriage is slideablymoved by rotation of the actuating screw, the at least one endplateramped surface slides against the at least one carriage ramped surfaceto cause the first endplate to move along an axis transverse to thelongitudinal axis, to increase a height of the spacer; and a secondendplate configured to engage a second bone of the joint.

In various embodiments thereof, the carriage includes a threaded boreinto which the actuating screw is threaded; the endplate is continuouslycurved along its length; the actuating screw is secured to the carriageby a nut; the nut and the carriage form a mating, curved bearing surfacetherebetween; the spacer further includes a screw support connected tothe frame and configured to rotatably retain the actuating screw; thescrew support forms a longitudinal axis, and the frame forms alongitudinal axis, the screw support being slideably connected to theframe to enable changing an angular orientation between the actuatingscrew and the frame.

In other embodiments thereof, the screw is rotatable at a plurality ofangular orientations of the actuating screw and the frame; the screwsupport is slideably connected to the frame by a flanged connection; thefirst endplate is connected to the frame by a slideable flangedconnection.

In another embodiment thereof, the spacer further includes a pinmoveable within a slot formed in the carriage; and a link pivotablymounted to the pin, and including a threaded bore into which theactuating screw is threadably engageable to cause the carriage toslideably move within the frame.

In yet further embodiments thereof, the first endplate is slideablyretained in connection with the frame by a flanged connection; thespacer further includes a screw support pivotally connected to the frameand rotatably supporting the actuating screw; the carriage includes atleast two ramped surfaces, and the second endplate includes at least oneramped surface mateable with at least one of the at least two rampedsurfaces of the carriage, whereby when the carriage is slideably movedby rotation of the actuating screw, the at least one second endplateramped surface slides against the at least one additional carriageramped surface to cause the second endplate to move along an axistransverse to the longitudinal axis to increase a height of the spacer.

In other embodiments thereof, the first endplate is configured to abutthe frame as the first endplate is moved along an axis transverse to thelongitudinal axis, whereby the first endplate moves substantially onlyalong an axis transverse to the longitudinal axis; at least one of thefirst endplate and the frame includes at least one aperture throughwhich a fastener may pass to secure the spacer to a bone of the joint;the spacer further includes a blocking mechanism to prevent backing outof a fastener passed through the first endplate; the first endplateincludes one or more projections configured to engage bone of the jointwhen the implant is positioned between bones of the joint.

In another embodiment of the disclosure, a method of separating bones ofa joint comprises inserting a spacer between bones of the joint, thespacer including a frame; a carriage slideably moveable in relation tothe frame, and having at least one ramped surface; an actuating screwconnected to the carriage and supported by the frame, the actuatingscrew configured to cause the carriage to slideably move in relation tothe frame when the actuating screw is rotated; a first endplateconfigured to engage a first bone of the joint, and having at least onesurface mateable with the at least one carriage ramped surface, wherebywhen the carriage is slideably moveable by rotation of the actuatingscrew, the at least one endplate ramped surface slides against the atleast one carriage ramped surface to cause the first endplate to movealong an axis transverse to the longitudinal axis, to increase a heightof the spacer; and a second endplate configured to engage a second boneof the joint.

In a yet further embodiment of the disclosure, a spacer for separatingbones of a joint comprises a frame; a carriage slideably moveable inrelation to the frame, and having at least two ramped surfaces; a screwsupport moveably connected to the frame to form a changeable angularorientation with respect to the frame; an actuating screw supported bythe screw support and connected to the carriage, the actuating screwconfigured to cause the carriage to slideably move in relation to theframe when the actuating screw is rotated; and first and secondendplates each configured to engage an opposing bone of the joint, eachhaving at least one ramped surface mateable with at least one of the atleast two carriage ramped surfaces, whereby when the carriage isslideably moved by rotation of the actuating screw, the at least oneramped surface of each of the first and second endplates slides againstthe at least one carriage ramped surface to cause the first and secondendplates to move relatively apart along an axis transverse to thelongitudinal axis, to increase a height of the spacer.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the disclosure, and the attendantadvantages and features thereof, will be more readily understood byreference to the following detailed description when considered inconjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a spacer implant of the disclosure, withan articulating screw support;

FIG. 2 depicts a cross section of the spacer of FIG. 1, taken through anactuating screw of the spacer, with the screw support orientedlongitudinally, as further illustrated in FIGS. 4 and 5;

FIG. 3 depicts the cross section of FIG. 2, with the spacer expanded bya separation of endplates;

FIG. 4 depicts the spacer of FIG. 3, taken along an orientation 90degrees offset from the orientation of the spacer of FIG. 3;

FIG. 5 depicts the spacer of FIG. 2, taken along an orientation 90degrees offset from the orientation of the spacer of FIG. 2;

FIG. 6 depicts a cross section through the spacer of FIG. 1;

FIG. 7 depicts the spacer of FIG. 6, the endplates relatively separated;

FIG. 8 depicts a cross section of an alternative spacer of thedisclosure shown in FIG. 14, the endplates separated by pushing acarriage, having a screw support aligned with a longitudinal axis of thespacer;

FIG. 9 depicts the spacer of FIG. 8, the endplates separated;

FIG. 10 depicts the spacer of FIG. 8, taken along an orientation 90degrees offset from the orientation of the spacer of FIG. 8;

FIG. 11 depicts the spacer of FIG. 10, the endplates separated;

FIG. 12 depicts the spacer of FIG. 11, the screw support disposed at anangle with respect to the frame;

FIG. 13 depicts the spacer of FIG. 10, the screw support disposed at anangle with respect to the frame;

FIG. 14 is a perspective view of an alternative embodiment of a spacerof the disclosure, including a carriage which is pushed to separateendplates, and an actuator screw which is displaced within a screwsupport;

FIG. 15 depicts the spacer of FIG. 14, the endplates separated;

FIG. 16 is a perspective view of an alternative spacer embodiment of thedisclosure, having a curved shape;

FIG. 17 depicts a cross section of the spacer of FIG. 16, the endplatesnot separated;

FIG. 18 depicts a cross section of the spacer of FIG. 16;

FIG. 19 is a perspective view of an alternative spacer embodiment of thedisclosure, the actuating screw secured to the carriage by a nut;

FIG. 20 depicts a top view of the spacer of FIG. 19; and

FIG. 21 is a cross section of the spacer of FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments are disclosed herein; however, it isto be understood that the disclosed embodiments are merely examples andthat the systems and methods described below can be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present subject matter in virtually anyappropriately detailed structure and function. Further, the terms andphrases used herein are not intended to be limiting, but rather, toprovide an understandable description of the concepts.

The terms “a” or “an”, as used herein, are defined as one or more thanone. The term plurality, as used herein, is defined as two or more thantwo. The term another, as used herein, is defined as at least a secondor more. The terms “including” and “having,” as used herein, are definedas comprising (i.e., open language).

With reference to FIGS. 1-3, the disclosure provides an expandablespacer 100 having an adjustable height. The implant is inserted betweentwo adjacent bony surfaces to facilitate separation of the bones, and ifdesired, can promote the fusion of the bony surfaces. Although intendedto be useful with any adjacent bony surface in which fusion is desired,the implant is advantageously applied to insertion between two adjacentvertebral bodies in any section of the spine, including the cervical,thoracic, lumbar, and sacral vertebral sections. More than one spacer100 may be implanted within the body, for example between successive orseparated vertebrae, between adjacent vertebrae. The use of multipleimplants is particularly advantageous for patients whose back pain isnot limited to a localized area, or for patients whose localized damagehas progressed to other areas of the spine.

The implant and methods for its insertion can be used in a treatmentprotocol for any of a wide variety of conditions in a patient involvingdiseased or damaged bony structures. The patient can be a human being.Additionally, it is contemplated that the implant may be useful inveterinary science for any animal having adjacent bony structures to befused. The implant can collapse, for example, to approximately one halfof an expanded size. When in this collapsed configuration, the implantcan be inserted into a space through a small incision and narrowpathways, using appropriate minimally-invasive techniques, and can bepositioned within the space between adjacent bones, and there expandedto a desired therapeutic height. The incision may be short, for exampleabout one inch in length, which is smaller than the implant in anexpanded configuration. If the desired position and/or expansion are notachieved, the implant can be collapsed, repositioned, and re-expanded insitu.

Although the implant is exemplified herein for use in the spine, theimplant is contemplated for fusion of any bony structures. While theimplants are described herein using several varying embodiments, theimplants are not limited to these embodiments. An element of oneembodiment may be used in another embodiment, or an embodiment may notinclude all described elements.

With reference to FIGS. 1-5, a spacer 100 of the disclosure includesendplates 102, 104 having expansion ramps 150, mateable with moveablelift ramps 250 of a carriage 200. In the embodiment shown, endplates102, 104 are symmetrical, and spacer 100 can be implanted with eitherendplate positioned superior with respect to the other. In otherembodiments, they may be dissimilar, and a particular orientation maythen be advantageous or necessary.

Spacer 100 forms a distal end 154 which is inserted first into the body,and which can be tapered to facilitate insertion between body tissue,and a proximal end 156, to which a tool may be connected. Distal andproximal ends 154 and 156 define a longitudinal plane 158, extendingtherebetween. To expand Spacer 100, lift ramps 250 are displacedrelative to endplates 102, 104, causing expansion ramps 150 to slidealong lift ramps 250, thereby moving endplates 102, 104 relativelyapart, thereby increasing a height of Spacer 100. Body tissue engagingprojections 152, for example tooth shaped projections, can be providedupon a surface of endplate 102, 104, to further secure spacer 100 in atherapeutic location.

Lift ramps 250 extend from carriage 200, which is slideably retainedwithin a frame 126 extending between endplates 102, 104. Carriage 200 isdisplaced relative to endplates 102, 104 by being pulled by a pin 106connected to a link 108 threadably connected to an actuating screw 110.One or more guide elements 112, associated with frame 126, can beprovided to prevent endplates 102, 104 from moving along longitudinalaxis 158 along with carriage 200, thereby causing lift ramps 250 andexpansion ramps 150 to be moved relative to each other, expanding orcontracting Spacer 100. Actuating screw can be prevented from movingalong longitudinal axis by a blocking flange 114 or 174.

With further reference to FIGS. 6-7, in accordance with the disclosure,an articulating screw support 160 is slideably retained in connectionwith frame 126 by, in one embodiment, a flanged connection 162. In thismanner, a longitudinal axis 168, defined by screw support 160 and pin106, may form a changeable angle (α) with respect to longitudinal axis158 of endplates 102, 104, or a longitudinal axis of frame 126.Actuating screw 110 is rotatably confined within screw support 160, andis threadably engaged with link 108. Pin 106 pivotally retains link 108in connection with carriage 200. A slot 202, associated with carriage200, enables movement of pin 106, whereby pin 106 and link 108 canmaintain a fixed orientation with respect to screw support 160,regardless of an angular disposition of screw support 160. Slot 202 isthus configured and dimensioned to enable a location of pin 106,confined therewithin, to correspond to a path of travel of screw support160 as defined by connection 162.

In one embodiment, a path of travel of screw support 160 is defined byconnection 162 to maintain a fixed orientation of carriage 200 withrespect to frame 126. More particularly, if screw support 160 is movedalong a path which does not pivot about a single point defined by acurrent location of pin 106, pin 106 may move within slot 202 tomaintain a fixed distance in a contracted position between pin 106 andscrew support 160, and therefore carriage 200 is not caused to be movedas screw support 160 is moved. In other embodiments, slot 202 is definedto cause a predetermined movement of carriage 200 as screw support 160is moved.

Similarly, regardless of a given orientation of screw support 160,rotation of actuating screw advances or retards link 108 and pin 106,causing movement of carriage 200 relative to endplates 102, 104. Moreparticularly, slot 202 defines a longitudinal axis 268, which isoriented to lie at a non-perpendicular angle (β) with respect tolongitudinal axis 168 of screw support 160, through a substantialportion of the range of motion of screw support 160. In this manner,once a desired orientation of screw support 160 has been established,rotation of actuating screw 110 causes pin 106 to push or pull along anedge of slot 202, thereby causing movement of carriage 200. If axis 168and 268 are perfectly perpendicular, it is possible no movement can becaused by threading screw 110; however, as a practical matter,reorienting screw support 160 a very small amount can resolve thistheoretical limitation. Carriage 200 is slideably retained by a channelor edge interface 116 formed between carriage 200 and at least oneendplate 102, 104, thereby limiting movement of carriage 200 alonglongitudinal axis 158.

With reference to FIGS. 8-15, an alternative spacer 100A of thedisclosure functions in analogous manner to the embodiment of FIGS. 1-7,however in this embodiment, rotation of actuating screw 110A causescarriage 200A to push endplates 102A, 104A to cause expansion. Moreparticularly, an orientation of expansion ramps 150A and lift ramps 250Aare oriented 180 degrees with respect to longitudinal axis 158. Theembodiment of FIGS. 8-9 additionally illustrates an alternativeactuating screw 110A configuration, in which screw 110A is rotatablyconnected to link 108A, and threadably connected within screw support160A, whereby screw 110A moves along longitudinal axis 168 within athreaded bore 118A of screw support 160A. Screw 110A causes movement oflink 108A, which advances or retards pin 106 within slot 202, to cause acorresponding movement of carriage 200A. As the various aspects ofdiffering embodiments of the disclosure may be substituted wherelogical, generally, it may be seen that this alternative screw 110Aconfiguration can be used with other embodiments of the disclosure, aswell.

As may be seen in FIG. 2, for example, in one embodiment, connection 162includes interlocking mating flanges 164, 166, associated with frame 126and screw support 160, respectively. Flanges 164, 166 form mutuallycurved guide surfaces defining a path of movement for screw support 160relative to frame 126, and retain screw support 160 in engagement withframe 126. Other configurations are possible, provided screw support 160and frame 126 may form different angular dispositions with respect toeach other, and wherein actuating screw 110 or 110A (FIG. 8) mayinteract with carriage 200 or 200A to slide carriage 200 or 200A withrespect to frame 126, 126A.

Turning now to FIGS. 16-18, spacer 100B includes curved endplates 102B,104B, and a curved carriage 200B slideable within edge interface 116B.Carriage 200B includes a threaded bore 218, into which actuating screw110B is threaded. As screw 110B is rotated in a first direction,carriage 200B is moved towards distal end 154, and as screw 110B isrotated in a second, opposite direction, carriage 200B is moved awayfrom distal end 154. Depending upon the angular direction of ramps 150Eand 250B, endplates 102B, 104B are moved together or apart, as describedwith respect to the embodiments of FIGS. 1 and 8. Spacer 100B forms,overall, a curved shape, which can advantageously be rotated as it isinserted through a minimal incision, to thereby become implanted betweenadjacent bones. This reduces an extent of a requirement of rotating aspacer, within the body, prior to insertion between the bones, thusreducing an adverse impact to adjacent body tissue.

As actuating screw 110B threads into carriage 200B, shaft 140 and head142 of screw 110B are angularly displaced with respect to screw support160B. Accordingly, screw support 160B is provided with a gapped region170, allowing movement of screw 110B. Additionally, screw support 160Bis retained in connection with a frame 126B by a flanged connection162B, in this case a dovetail connection. Connection 162B enables screwsupport 160B to be angled with respect to frame 126B, to facilitateaccess to screw 110B by a tool (not shown), when spacer 100B isimplanted within the body, and to further enable screw 110B to change anangle with respect to frame 126B.

Frame 126B is connected to each of endplates 102B, 104B by a flangedconnector, in this embodiment a dovetail formed between endplate flanges178 extending from each of endplates 102B, 104B, and frame flanges 180associated with an intermediate connector 182. Actuating screw 110B canbe rotatably retained within screw support 160B by a washer or flange(not shown) positioned in groove 186 within screw support 160B, orintermediate connector 182 can be configured to rotatably retain screw100B.

With reference to FIGS. 16-21, a spacer 100C functions in a similarmanner to spacers 100, 100A, and 100B, with the following distinctions.Initially, in the embodiment shown, screw support 160C does not slidealong a flanged connector 162, and is connected to endplates 102C, 104Cin a like manner as spacer 100B. However, screw support 160C could beconnected to a remainder of spacer 100C using a flange connector 162.Additionally, actuating screw 110C has a tool engagement 188C that isdifferent than the tool engagement of other embodiments, althoughengagement style 188, or any other style tool engagement, may beprovided upon screw 110C. Engagement stylet 188 allows for articulatingbetween the holder and the implant by pivot point 192.

As may best be seen in FIG. 20, 21, nut 198 retains actuating screw 110Cin connection with carriage 200C. However, in distinction with respectto threaded bore 218 of spacer 100B, nut 198 may toggle, or change anangular orientation with respect to carriage 200C, as screw 100C isrotated, and carriage 200C is moved. Nut 198 can be provided with a nutbearing surface 198′, which mateably interacts with a carriage bearingsurface 208. Similar bearing surfaces 198″ and 208′ can be provided onan opposite side of nut 198, for pushing carriage 200C in an oppositedirection. In the embodiment shown, threading nut 198 in the directionof proximal end 156 causes an expansion or increase in height of spacer100C, and threading nut 198 in a direction of distal end 154 causes areduction, or decrease in height of spacer 100C. However, ramps 150C and250C can be oriented to cause an opposite effect.

The following discussion pertains to all embodiments of the disclosure,including spacers 100, 100A, 100B, and 100C. For brevity, the lettersuffix designating variations of like parts will be omitted, unless aspecific distinction is made. For all spacer 100 embodiments of thedisclosure, carriage 200 can be slid, or actuated, when screw support 60is disposed at an angle with respect to the carriage. In the embodimentsof FIGS. 1-15, this angle may vary between 0° and 70°, and withmodifications, this angle could be increased to a theoretical maximumapproaching 180°. The embodiment of FIGS. 16-18 accomplishes disposingscrew 100B at an angle to the endplate bodies by curving the endplates,and by configuring bore 218 at an angle with respect to carriage 200B.

In all embodiments, head 142 of screw 110 may be accessed by a drivingtool extending from outside the body, into the body, while endplates102, 104 lie at an angle, for example perpendicular, to a pathway intothe body. More particularly, spacers 100 of the disclosure may beinserted between vertebral bodies when in a collapsed or non-expandedstate, from any approach to the spine. As spacer 100 is inserted betweenendplates, it is rotated to contact cortical bone of the endplates, andto avoid anatomical structures which should not be disturbed.

Once rotated into position, screw support 160 can be turned towards anexterior of the body, if it has not already been so turned, whereby atool may be conveniently mated with a tool engagement 188 of screw head142. After screw 110 is rotated, endplates 102, 104 separate, expandingor increasing a height of spacer 100, and restoring and maintaining atherapeutic spacing between adjacent bones. In some embodiments, afterexpansion of spacer 100, screw support 160 may slide along flangedconnection 162 to lie at an optimal orientation with respect to bodytissue, for example 0 degrees with respect to carriage 200, or at anangle deemed best by the medical practitioner.

Spacers 100 may include ramps 150, 250 of differing height within aspacer, whereby endplates 102, 104 mutually separate at different ratesat distal and proximal ends 154, 156, or at sides transverse to distaland proximal ends 154, 156, whereby an angular disposition of adjacentbones may be changed, for example to correct lordosis or scoliosis.Endplates 102, 104 may additionally, or alternatively, be resilient, sothat they may conform to bony surfaces, forming a more stable supportplatform. Accordingly, endplates 102, 104 can be fabricated from apolymeric material, a naturally resilient material, or a resilientmetal, for example a shape memory alloy, or any other resilientbiocompatible material of sufficient strength and durability forseparating bones within the body. Spacers 100 may further be removed orrepositioned during an initial implantation procedure, or later in time.

In accordance with the disclosure, during implantation of intervertebralspacers from a posterior approach, there is a need to avoid damagingnerve roots. A prior art spacer dimensioned to separate bones can blocka view of nerve roots as it is inserted, and due to its large size,poses a greater risk of contacting nerve roots during insertion into thebody. As a result, the medical practitioner must more often retractnerve roots, with attendant danger of tissue damage. Spacers 100 of thedisclosure form a smaller dimension during implantation, relative to afinal dimension for spacing bones. Accordingly, nerve roots can bevisualized and avoided during insertion, and nerve root manipulation canbe avoided or minimized.

As spacers 100 of the disclosure can be articulated during implantation,they can be inserted between bones by being passed through a minimallyinvasive entry, for example through an incision approximating thesmallest collapsed dimension, for example transverse to a longitudinaldimension extending between distal and proximal ends 154, 156. Thisenables exceptional anterior placement without impaction, as well asfacilitating implantation from other approaches. Implants of thedisclosure further develop a good bone contact area, as an implant witha larger footprint may be inserted through a reduced size incision, dueto the overall dimensions of the implant being reduced during insertion.

Spacers 100 of the disclosure enable a continuous expansion andretraction over a range of displacements according to predetermineddimensions of a specific spacer design. This provides the ability todistract vertebral bodies or other bones to a desired height orseparation. Endplates 102, 104 can be shaped to form planes or surfaceswhich converge relative to each, to provide for proper lordosis, and canbe provided with openings 190 through which bone may grow, and intowhich bone graft material may be placed. Spacers 100 of the disclosuremay be used to distract, or force bones of a joint apart, or may be usedto maintain a separation of bones created by other means, for example bya retractor. Endplates may additionally be curved to conform to thesurface of body tissue, for example the surface of cortical bone, of thevertebra to be contacted, for improved fixation and load bearing.

Spacers 100 of the disclosure may be further secured in connection withthe body by passage of elongated fasteners through frame 126, or anendplate 102, 104. As described therein, a blocking mechanism can beused to prevent backing out of the elongated fastener. Similarly, screw110 can be provided with a blocking mechanism as described in theforegoing reference, or a resilient washer (not shown) may be positionedwithin groove 186, to resist unintended rotation of screw 110.

Implants of the disclosure may be fabricated using any biocompatiblematerials known or hereinafter discovered, having sufficient strength,flexibility, resiliency, and durability for the patient, and for theterm during which the device is to be implanted. Examples include butare not limited to metal, such as, for example titanium and chromiumalloys; polymers, including for example, PEEK or high molecular weightpolyethylene (HMWPE); and ceramics. There are many other biocompatiblematerials which may be used, including other plastics and metals, aswell as fabrication using living or preserved tissue, includingautograft, allograft, and xenograft material.

Portions or all of the implant may be radiopaque or radiolucent, ormaterials having such properties may be added or incorporated into theimplant to improve imaging of the device during and after implantation.

Spacers 100 may be formed using titanium, or a cobalt-chrome-molybdenumalloy, Co—Cr—Mo, for example as specified in ASTM F1537 (and ISO5832-12). The smooth surfaces may be plasma sprayed with commerciallypure titanium, as specified in ASTM F1580, F1978, F1147 and C-633 (andISO 5832-2). Alternatively, part or all of spacers 100 may be formedwith a polymer, for example ultra-high molecular weight polyethylene,UHMWPE, for example as specified in ASTM F648 (and ISO 5834-2). In oneembodiment, PEEK-OPTIMA (a trademark of Invibio Ltd Corp, UnitedKingdom) may be used for one or more components of the implants of thedisclosure. For example, polymeric portions can be formed withPEEK-OPTIMA, which is radiolucent, whereby bony ingrowth may beobserved. Other polymeric materials with suitable flexibility,durability, and biocompatibility may also be used.

In accordance with the invention, implants of various sizes may beprovided to best fit the anatomy of the patient. Components of matchingor divergent sizes may be assembled during the implantation procedure bya medical practitioner as best meets the therapeutic needs of thepatient, the assembly inserted within the body using an insertion tool.Implants of the invention may also be provided with an overall angulargeometry, for example an angular mating disposition of endplates, toprovide for a natural lordosis, or a corrective lordosis, for example offrom 0° to 12° for a cervical application, although much differentvalues may be advantageous for other joints. Lordotic angles may also beformed by shaping one or both endplates to have relatively non-coplanarsurfaces.

Expanded implant heights, for use in the cervical vertebrae for example,may typically range from 7 mm to 12 mm, but may be larger or smaller,including as small as 5 mm, and as large as 16 mm, although the size isdependent on the patient, and the joint into which an implant of theinvention is to be implanted. Spacers 100 may be implanted within anylevel of the spine, and may also be implanted in other joints of thebody, including joints of the hand, wrist, elbow, shoulder, hip, knee,ankle, or foot.

In accordance with the invention, a single spacer 100 may be used, toprovide stabilization for a weakened joint or joint portion.Alternatively, a combination of two, three, or more of any of spacer 100may be used, at a single joint level, or in multiple joints. Moreover,implants of the disclosure may be combined with other stabilizing means.

Additionally, spacers 100 of the disclosure may be fabricated usingmaterial that biodegrades in the body during a therapeuticallyadvantageous time interval, for example after sufficient bone ingrowthhas taken place. Further, implants of the disclosure are advantageouslyprovided with smooth and or rounded exterior surfaces, which reduce apotential for deleterious mechanical effects on neighboring tissues.

Any surface or component of an implant of the disclosure may be coatedwith or impregnated with therapeutic agents, including bone growth,healing, antimicrobial, or drug materials, which may be released at atherapeutic rate, using methods known to those skilled in the art.

Devices of the disclosure provide for adjacent vertebrae to be supportedduring flexion/extension, lateral bending, and axial rotation. In oneembodiment, spacer 100 is indicated for spinal arthroplasty in treatingskeletally mature patients with degenerative disc disease, primary orrecurrent disc herniation, spinal stenosis, or spondylosis in thelumbosacral spine (LI-SI). Degenerative disc disease is advantageouslydefined as discogenic back pain with degeneration of the disc confirmedby patient history and radiographic studies, with or without leg(radicular) pain. Patients are advantageously treated, for example, whomay have spondylolisthesis up to Grade 1 at the involved level. Thesurgery position spacer 100 may be performed through an Anterior,Anterolateral, Posterolateral, lateral or any approach.

In a typical embodiment, spacer implants of the disclosure have anuncompressed height, before insertion, of 7 to 13 mm, and mayadvantageously be provided in cross-sections of 10×27 mm, 12×32 mm and12×37 mm, with 4, 8, 12, or 16 degree lordotic angles, although theseare only representative sizes, and substantially smaller or larger sizescan be therapeutically beneficial. In one embodiment implants inaccordance with the instant disclosure are sized to be inserted using anMIS approach, for example using a reduced incision size, for exampleless than about 5 cm, and advantageously less than about 2.5 cm, withfewer and shorter cuts through body tissue. Spacer 100 mayadvantageously be used in combination with other known or hereinafterdeveloped forms of stabilization or fixation, including for example rodsand plates.

Spacer implants of the disclosure can be inserted into the body,advantageously in a contracted or non-expanded configuration, through atransforaminal approach, and can articulate in attachment to an insertertool (not shown), for example for anterior placement. Once placement isachieved, the implant is capable of expanding for disc heightrestoration. To maintain an engagement spacer 100 and an insertion tool,a driving end (not shown) of the tool is inserted into tool engagement188. To prevent separation of the tool and spacer 100, a tool connector192 may be provided, extending from or formed within screw support 60.In the embodiment shown in FIG. 16, for example, tool connector 192extends from a surface of screw support 60B, and is releaseably graspedby a mating tool portion.

Portions of spacer 100 may be radiopaque or radiotransparent. To improvevisibility under imaging, radiopaque elements 194 may be provided inpredetermined locations within spacer 100. In the embodiment of FIG. 16,for example, elements 194 are positioned within at least one of endplate102B, 104B.

Implant spacers 100 of the disclosure can be positioned anterioriorlyand continuously expanded to provide axial balance and greater endplatecontact area, and allow for superior sagittal correction, and areinsertable into the body through a smaller window, decreasing the needfor damage and trauma to body tissue. Spacers 100 of disclosure providethe benefits of an ALIF device, implantable through a familiar posteriorapproach, decreasing surgery time and associated blood loss, as well aseliminating the need for an access surgeon.

All references cited herein are expressly incorporated by reference intheir entirety. There are many different features to the presentinvention and it is contemplated that these features may be usedtogether or separately. Unless mention was made above to the contrary,it should be noted that all of the accompanying drawings are not toscale. Thus, the invention should not be limited to any particularcombination of features or to a particular application of the invention.Further, it should be understood that variations and modificationswithin the spirit and scope of the invention might occur to thoseskilled in the art to which the invention pertains. Accordingly, allexpedient modifications readily attainable by one versed in the art fromthe disclosure set forth herein that are within the scope and spirit ofthe present invention are to be included as further embodiments of thepresent invention.

What is claimed is:
 1. A spacer for separating bones of a joint, thespacer comprising: a frame; a carriage slideably moveable in relation tothe frame, and having at least one ramped surface; an actuating screwconnected to the carriage and supported by the frame, the actuatingscrew configured to cause the carriage to slideably move in relation tothe frame when the actuating screw is rotated; a first endplateconfigured to engage a first bone of the joint, and having at least oneramped surface mateable with the at least one carriage ramped surface,whereby when the carriage is slideably moved by rotation of theactuating screw, the at least one endplate ramped surface slides againstthe at least one carriage ramped surface to cause the first endplate tomove along an axis transverse to a longitudinal axis, to increase aheight of the spacer; and a second endplate configured to engage asecond bone of the joint, a screw support connected to the frame andconfigured to retain the actuating screw wherein the screw support isconfigured to change an angular orientation between the actuating screwand the frame.
 2. The spacer of claim 1, wherein the first endplate iscontinuously curved along its length.
 3. The spacer of claim 1, whereinthe screw support is rotatable at a plurality of angular orientationswith respect to the frame.
 4. The spacer of claim 1, wherein the screwsupport is slideably connected to the frame by a flanged connection. 5.The spacer of claim 1, wherein the first endplate is connected to theframe by a slideable flanged connection.
 6. The spacer of claim 1,further including: a pin moveable within a slot formed in the carriage;and a link pivotably mounted to the pin, and including a threaded boreinto which the actuating screw is threadably engageable to cause thecarriage to slideably move within the frame.
 7. The spacer of claim 1,wherein the first endplate is slideably retained in connection with theframe by a flanged connection.
 8. The spacer of claim 1, furtherincluding the screw support pivotally connected to the frame androtatably supporting the actuating screw.
 9. The spacer of claim 1,wherein the carriage includes at least a second ramped surface, and thesecond endplate includes at least one ramped surface mateable with atleast one of the at least two ramped surfaces of the carriage, wherebywhen the carriage is slideably moved by rotation of the actuating screw,the at least one second endplate ramped surface slides against thesecond ramped surface to cause the second endplate to move along theaxis transverse to the longitudinal axis to increase a height of thespacer.
 10. The spacer of claim 1, the first endplate is configured toabut the frame as the first endplate is moved along the axis transverseto the longitudinal axis, whereby the first endplate moves substantiallyonly along the axis transverse to the longitudinal axis.
 11. The spacerof claim 1, wherein at least one of the first endplate and the frameincludes at least one aperture through which a fastener may pass tosecure the spacer to a bone of the joint.
 12. The spacer of claim 1,wherein the first endplate includes one or more projections configuredto engage bone of the joint when the spacer is positioned between bonesof the joint.
 13. A method of separating bones of a joint, comprising:inserting a spacer between bones of the joint, the spacer including: aframe a carriage slideably moveable in relation to the frame, and havingat least one ramped surface; an actuating screw connected to thecarriage and supported by the frame, the actuating screw configured tocause the carriage to slideably move in relation to the frame when theactuating screw is rotated; a first endplate configured to engage afirst bone of the joint, and having at least one ramped surface mateablewith the at least one carriage ramped surface, whereby when the carriageslideably moves by rotation of the actuating screw, the at least oneendplate ramped surface slides against the at least one carriage rampedsurface to cause the first endplate to move to increase a height of thespacer; and a second endplate configured to engage a second bone of thejoint, a screw support pivotally connected to the frame and rotatablesupporting the actuating screw.
 14. A spacer for separating bones of ajoint, the spacer comprising: a frame; a carriage slideably moveable inrelation to the frame, and having at least two ramped surfaces; a screwsupport moveably connected to the frame, the screw support capable ofchanging angular orientation with respect to the frame; an actuatingscrew supported by the screw support and connected to the carriage, theactuating screw configured to cause the carriage to slideably move inrelation to the frame when the actuating screw is rotated; and first andsecond endplates each configured to engage an opposing bone of thejoint, each endplate having at least one ramped surface mateable with atleast one of the at least two carriage ramped surfaces, whereby when thecarriage is slideably moved by rotation of the actuating screw, the atleast one ramped surface of each of the first and second endplates pushagainst the at least one carriage ramped surface to cause the first andsecond endplates to move relatively apart to increase a height of thespacer.